Photocurable pigment type inkjet ink composition

ABSTRACT

A photocurable pigment type inkjet ink composition including 5 to 95 wt % of water; 0.5 to 20 wt % of a pigment; 1 to 70 wt % of a photocurable component; and 0.0001 to 30 wt % of a reactive surfactant. The reactive surfactant can serve as a pigment dispersant for dispersing pigment particles or as an emulsifier for emulsifying the photocurable component.

This application is a continuation-in-part of application Ser. No.10/705,943 filed on Nov. 13, 2003, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photocurable pigment type inkjet inkcomposition, and more particularly to a photocurable pigment type inkjetink composition including a reactive surfactant.

2. Description of the Related Art

Early inkjet printers used water-based ink that included thewater-soluble solvent. The inkjet printing method involves printing awater-based ink onto an ink-absorbent substrate, such as paper or asubstrate coated with an ink-receiver layer. The printed image is fixedby penetration, absorption and drying of the ink. Water-based inksuffers from long drying time and it cannot be printed on anon-ink-absorbent substrate such as a glass, plastic, metal, or ceramicsubstrate. In addition, the printed image has poor water fastness andmay partially dissolve upon contact with moisture.

A photo-curable type (ultraviolet-curable type) inkjet ink has beendeveloped to improve the above-mentioned disadvantages. A photo-curabletype inkjet ink includes at least a pigment, a dispersant for thepigment, a photocurable (photopolymerizable) component (such as amonomer, resin, or oligomer), an emulsifier for emulsifying thephotocurable component, and a photoinitiator that is introduced into theink by emulsion or dissolution. The photo-curable type inkjet ink isprinted onto a substrate and fixed after irradiation (UV ray, IR ray, orelectron beam). Thus, a printed image can be fixed on ink-absorbentsubstrates, and also non-ink-absorbent substrates such as glass,plastic, metal, or ceramic substrates. Thus, the adhesion of the pigmentto the substrate, and the water fastness and smear resistance of theimage are improved.

Generally, in a pigment type inkjet ink, the average particle size ofthe pigment is less than 200 nm. Therefore, a suitable dispersanttogether with milling equipment must be used to turn the pigmentparticles into microparticles suitable for inkjet printing. Themicroparticle pigment dispersant solution requires good dispersionstability to prevent nozzle clogging due to pigment agglomeration duringprinting. In addition, a photocurable component must be blended into theink by emulsion or dissolution.

Both the dispersant for dispersing the pigment and the emulsifier foremulsifying the photocurable component affect the surface tension andthe viscosity of the ink, which in turn affects the inkjet printingproperties of the ink.

R.O.C. Patent No. 271464 discloses a dispersant that can dissolve thephotocurable resin. Japanese Patent No. 09165540, U.S. Pat. No.5,952,401, and Japanese Patent No. 2001288386 also disclosenon-photocurable dispersants. U.S. Pat. No. 6,326,419 uses anon-photocurable emulsifier for emulsifying a UV-curable monomer oroligomer.

In the above conventional techniques, the dispersants and emulsifiersused in the photocurable inkjet ink are non-photocurable (non-reactive),that is, they cannot react by irradiation. Therefore, the non-reactivedispersant or emulsifier remains in the printed image and acts as aplasticizer. This adversely affects the adhesion of the printed image tothe substrate, and the smear resistance of the printed image.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to improve theabove-mentioned problems and provide a photocurable pigment type inkjetink composition with good inkjet printing and film forming properties,and good water fastness.

To achieve the above object, the photocurable pigment type inkjet inkcomposition of the present invention includes 5 to 95 wt % of water; 0.5to 20 wt % of a pigment; 1 to 70 wt % of a photocurable component; and0.0001 to 30 wt % of a reactive surfactant, wherein the reactivesurfactant comprises a terminal C═C double bond, and can be ionic ornon-ionic surfactant. Preferably, the reactive surfactant is present inan amount of 0.5 to 15 wt %.

BRIEF DESCRIPTION OF THE DRAWING

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the office upon request and paymentof the necessary fee.

FIG. 1 is a drop formation diagram of the ejected ink droplet of inkprepared from Example 1 of the present invention.

FIG. 2 is a drop formation diagram of the ejected ink droplet of inkprepared from Example 3 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The reactive surfactant of the present invention can be a dispersant fordispersing the pigment particles, or an emulsifier for emulsifying thephotocurable component. Specifically, the reactive surfactant comprisesa terminal C═C double bond, and can be ionic or non-ionic surfactant. Inembodiments of the invention, the reactive surfactant can be preferableacrylic reactive surfactant comprising terminal C═C double bond orderivatives thereof, such as bis(polyoxyethylene polyphenyl ether)methacryl sulfate ammonium, and polyoxyethylene allyl nonylphenolsulfonate.

The feature of the present invention is to use a reactive surfactant toserve as a dispersant for dispersing the pigment particles, or anemulsifier for emulsifying the photocurable component (a monomer,oligomer, or resin). Therefore, during the ink preparation andapplication processes, the reactive surfactant transforms the pigmentinto sub-micro or nano particles with good dispersion stability andemulsifies the photocurable component.

In addition to the above components, the photocurable pigment typeinkjet ink composition of the present invention can further include 0.05to 15 wt % of a photoinitiator, preferably in an amount of 0.1 to 10 wt%. At this time, the reactive surfactant can simultaneously emulsify thephotocurable component and the photoinitiator.

The reactive surfactant suitable for use in the present invention can bephotocurable, for example, one containing a C═C double bond forundergoing free radical polymerization. Preferably, the C═C double bondcan be present at a terminal end of molecule chain of the reactivesurfactant, for example, at an end group of the main chain or side chainin order to increase reactivity. The reactive surfactant can be ionic ornon-ionic surfactant, and suitable non-ionic surfactant for use in thepresent invention can have a hydrophilic hydrophobic balance (HLB) valueof 8 to 16, preferably 12 to 16.

The photocurable pigment type inkjet ink composition of the presentinvention can have a surface tension of 20 to 65 mN/m, preferably 20 to40 mN/m.

The photocurable ink of the present invention can be successfullyprinted on a non-ink-absorbent substrate, such as a glass, plastic,metal, or ceramic substrate. After curing, the printed image has goodstability, film-forming property, and water fastness. Moreover, when theink is inkjet printed and irradiated by UV, the reactive surfactant hasreactive functional groups that can participate in the polymerization(photocuring reaction) of other monomers and oligomers. This canincrease the preservation and physical properties of the printed imagewithout causing the conventional plasticized side effect due to use of anon-reactive surfactant.

Example 1 Using a Reactive Surfactant as an Emulsifier for thePhotocurable Resin and Photoinitiator

33 g of a red pigment (Pigment Red 254), 9.9 g of a non-reactive pigmentdispersant (Sinonate 9620P from Sino-Japan Chemical Co. Ltd.), 9.9 g ofstyrene/acrylic acid block copolymer dispersant (ST/AA=1/1, molecularweight is about 3200), 167.2 g of water, and 644 g of glass millingbeads were added and milled for 10 hours. After filtration, a pigmentconcentrate DBR006 with 8.6% solid content was prepared. The surfacetension measured by Kruss K7 was 46.5 mN/m, the viscosity determined byBrook Field DVII was 3.02 cps, and the pigment average particle sizedetermined by Malvern Particle Sizer was 69.7 nanometers.

2-hydroxy-2-methyl-1-phenyl-propan-1-one (photoinitiator, 1.8 weightparts), polyethylene glycol (200) diacrylate (photocurable compound, 20weight parts), and ethoxylated (9) trimethylolpropane (photocurablecompound, 1.5 weight parts) were stirred for 10 minutes. 2-pyrrolidone(co-solvent, 5 weight parts) and anionic reactive surfactantbis(polyoxyethylene polyphenyl ether) methacryl sulfate ammonium (10weight parts, from Sino-Japan Chemical Co. Ltd.) the composition isbis(polyoxyethylene polyphenyl ether)methacryl sulfate ammonium salt) asan emulsifier were then added and stirred for 10 minutes. 50 weightparts of water was then added and stirred at 5000 rpm for 5 minutes. Thereaction mixture was held still until bubbles disappeared. The redpigment concentrate DBRO06 (15 weight parts) was then added and stirredfor 15 minutes to obtain a photocurable inkjet ink. The ink had asurface tension of 38 mN/m and a viscosity of 18.4 cps.

The above ink was charged in a HP51626 ink cartridge and printed on aglass with a HP420 inkjet printer. The printed glass was baked at 90° C.for 30 minutes, then at 150° C. for 1 hour, and then irradiated by UVlight for 50 seconds. The image could be fixed on the non-ink-absorbentglass.

The jetting speed of the ink was 6 m/s. The drop formation diagram wasshown in FIG. 1. Using the reactive surfactant as an emulsifier of thephotocurable resin and the photoinitiator, the photocurable inkjet inkexhibits good jetting properties.

A. UV Curing Reactivity:

The printed image on glass was cured by UV and tested by the cross-cutmethod.

Grade 5: 100% adhesion

Grade 4: 80% adhesion (20% peeling)

Grade 3: 60% adhesion (40% peeling)

Grade 2: 40% adhesion (60% peeling)

Grade 1: 20% adhesion (80% peeling)

B. Water Fastness:

The image was printed on glass and cured by UV. Then the image wasimmersed in water at 25° C. for 5 minutes, and then tested.

Grade 5: 100% adhesion

Grade 4: 80% adhesion (20% peeling)

Grade 3: 60% adhesion (40% peeling)

Grade 2: 40% adhesion (60% peeling)

Grade 1: 20% adhesion (80% peeling)

The results for UV curing reactivity and water fastness are shown inTable 1.

Example 2 Using a Reactive Surfactant as an Emulsifier for thePhotocurable Resin and Photoinitiator

2-hydroxy-2-methyl-1-phenyl-propan-1-one (photoinitiator, 1.8 weightparts), polyethylene glycol (200) diacrylate (photocurable compound, 20weight parts), and ethoxylated (9) trimethylolpropane (photocurablecompound, 1.5 weight parts) were stirred for 10 minutes. 2-pyrrolidone(co-solvent, 5 weight parts) and reactive surfactant polyoxyethyleneallyl nonylphenol sulfonate (5 weight parts, from HSIN SOU Chemical Co.,Ltd.) as an emulsifier were then added and stirred for 10 minutes. 50weight parts of water was then added and stirred at 5000 rpm for 5minutes. The reaction mixture was held still until bubbles disappeared.The red pigment concentrate DBR006 (15 weight parts) prepared fromExample 1 was then added and stirred for 15 minutes to obtain aphotocurable inkjet ink.

The above ink was charged in a HP51626 ink cartridge and printed on aglass with a HP420 inkjet printer. The printed glass was baked at 90° C.for 30 minutes, then at 150° C. for 1 hour, and then irradiated by UVlight for 50 seconds. The image was fixed on the non-ink-absorbentglass.

The test results for UV curing extent and water fastness are shown inTable 1.

Example 3 Using a Reactive Dispersant for Pigment Grinding

27.75 g of a red pigment (Pigment Red 254), 12.3 g of a reactivedispersant bis(polyoxyethylene polyphenyl ether) methacryl sulfateammonium (from Sino-Japan Chemical Co. Ltd.), 299 g of glass millingbeads, and 146 g of water were moistened, milled for 10 hours, andfiltered, obtaining a pigment concentrate NDR004 with 11.11% solidcontent. Physical properties: pH=7.56, viscosity=2.91 cps, surfacetension=42.5 mN/m, average particle size=65.4 nanometers.

2-hydroxy-2-methyl-1-phenyl-propan-1-one (photoinitiator, 1.8 weightparts), polyethylene glycol (200) diacrylate (photocurable compound, 20weight parts), and ethoxylated (9) trimethylolpropane (photocurablecompound, 1.5 weight parts) were stirred for 10 minutes. A non-reactiveemulsifier and 2-pyrrolidone (co-solvent, 5 weight parts) were thenadded and stirred for 10 minutes. 50 weight parts of water was thenadded and stirred at 5000 rpm for 5 minutes. The reaction mixture washeld still until bubbles disappeared. The pigment concentrate NDR004containing the reactive dispersant (15 weight parts) was then added andstirred for 5 minutes to obtain a photocurable inkjet ink. Surfacetension=44 mN/m, viscosity=14.7 cps.

The above ink was charged in a HP51626 ink cartridge and printed on aglass with a HP420 inkjet printer. The printed image was baked at 90° C.for 30 minutes, then at 150° C. for 1 hour, and irradiated by UV lightfor 45 seconds. The image was fixed on the non-ink-absorbent glass.

The jetting speed of the ink was 10 m/s. The drop formation diagram wasshown in FIG. 2. Using the reactive dispersant to mill the pigment, thephotocurable inkjet ink exhibits good jetting properties.

The test results for UV curing reactivity and water fastness are shownin Table 1.

Comparative Example 1 Using a Non-reactive Surfactant as an emulsifierfor Photocurable Resin and Photoinitiator

2-hydroxy-2-methyl-1-phenyl-propan-1-one (photoinitiator, 1.8 weightparts), polyethylene glycol (200) diacrylate (photocurable compound, 20weight parts), and ethoxylated (9) trimethylolpropane (photocurablecompound, 1.5 weight parts) were stirred for 10 minutes. 2-pyrrolidone(co-solvent, 5 weight parts) and sodium dodecylbenzenesulfonate(non-reactive surfactant as an emulsifier, 20 weight parts) were addedand stirred for 10 minutes. 50 weight parts of water was then added andstirred at 5000 rpm for 5 minutes. The reaction mixture was held stilluntil bubbles disappeared. The red pigment concentrate DBR006 preparedfrom Example 1 (15 weight parts) was then added and stirred for 15minutes to obtain a photocurable inkjet ink.

The above ink was charged in a HP51626 ink cartridge and printed on aglass by a HP420 inkjet printer. The printed glass was baked at 90° C.for 30 minutes, then at 150° C. for 1 hour, and irradiated by UV lightfor 50 seconds.

The test results for UV curing reactivity and water fastness are shownin Table 1.

TABLE 1 UV-curing reactivity (film forming Water Example DispersantEmulsifier property) fastness Example 1 Non-reactive Reactive >Grade4 >Grade 3 (bis(polyoxyethylene polyphenyl ether) methacryl sulfateammonium) Example 2 Non-reactive Reactive >Grade 4 >Grade 3(Polyoxyethylene allyl nonylphenol sulfonate) Example 3 ReactiveNon-reactive >Grade 4 >Grade 3 (bis(polyoxyethylene polyphenyl ether)methacryl sulfate ammonium) Comparative Non-reactive Non-reactive Grade2 Grade 1 Example 1

As shown in Table 1, the photocurable jet ink of the present inventionprepared by the reactive surfactant as either an emulsifier for thephotocurable composition or a dispersant for pigment grinding has abetter film-forming property and water fastness.

The foregoing description of the preferred embodiments of this inventionhas been presented for purposes of illustration and description. Obviousmodifications or variations are possible in light of the above teaching.The embodiments chosen and described provide an excellent illustrationof the principles of this invention and its practical application tothereby enable those skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. All such modifications and variations arewithin the scope of the present invention as determined by the appendedclaims when interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

1. A photocurable pigment inkjet ink composition comprising: 5 to 95 wt% of water; 0.5 to 20 wt % of a pigment; 0.05 to 15 wt % of aphotoinitiator; 1 to 70 wt % of a photocurable component; and 0.0001 to30 wt % of a reactive surfactant, wherein the reactive surfactantcomprises a compound containing a terminal C═C double bond and is anemulsifier for emulsifying the photocurable component and thephotoinitiator, and wherein the reactive surfactant comprisesbis(polyoxyethylene polyphenyl ether) methacryl sulfate ammonium, orpolyoxyethylene allyl nonylphenol sulfonate.
 2. The photocurable pigmentinkjet ink composition as claimed in claim 1, wherein the reactivesurfactant comprise acrylic reactive surfactant containing a terminalC═C double bond or derivatives thereof.
 3. The photocurable pigmentinkjet ink composition as claimed in claim 1, wherein the reactivesurfactant is non-ionic reactive surfactant and has a hydrophilichydrophobic balance (HLB) value of 8 to
 16. 4. The photocurable pigmentinkjet ink composition as claimed in claim 3, wherein the reactivesurfactant is non-ionic reactive surfactant and has a hydrophilichydrophobic balance (HLB) value of 12 to
 16. 5. The photocurable pigmentinkjet ink composition as claimed in claim 1, wherein the reactivesurfactant is present in an amount of 0.5 to 15 wt %.
 6. Thephotocurable pigment inkjet ink composition as claimed in claim 1,wherein the composition has a surface tension of 20 to 65 mN/m.
 7. Thephotocurable pigment inkjet ink composition as claimed in claim 6,wherein the composition has a surface tension of 20 to 40 mN/m.
 8. Thephotocurable pigment inkjet ink composition as claimed in claim 1,wherein the reactive surfactant is a pigment dispersant for dispersingpigment particles.
 9. The photocurable pigment inkjet ink composition asclaimed in claim 1, wherein the reactive surfactant is an emulsifier foremulsifying the photocurable component.
 10. A photocurable pigmentinkjet ink composition comprising: 5 to 95 wt % of water; 0.5 to 20 wt %of a pigment; 1 to 70 wt % of a photocurable component; and 0.0001 to 30wt % of a reactive surfactant, wherein the reactive surfactant comprisesbis(polyoxyethylene polyphenyl ether) methacryl sulfate ammonium, orpolyoxyethylene allyl nonylphenol sulfonate.